House Plant Care: Bringing Plants in for the Fall

If your house plants spent the summer outside, they may have picked up a few friends. In addition, with the favorable growing conditions outside—increased light, humidity, and air circulation—your plants may have gotten a little too big or unshapely over the growing season. Here are some tips on house plant care as plants return to the unnatural environment of the great indoors.

A little judicious pruning may be all your plants need. However, it is a jungle out there.

CHECK YOUR PLANTS carefully (leaves and stems) for signs of plant pests such as mealybug, scale insects, mites, aphids, caterpillars, etc. If you see pests, or find pest damage, like chewed or stippled leaves, insect droppings, sticky leaves, or webbing, treat plants before bringing them inside (start early and watch the weather).

Before bringing out the chemicals, try a few simple home remedies. For easily dislodged insects like aphids, crickets, Daddy-longlegs, or spiders, try spraying them off with a stream or spray of water from the hose. Caterpillars and grasshoppers can be picked off by hand. Snails and slugs are usually active at night, so use a flashlight to catch them at work, and remove them by hand, also.

Critters that have taken up residence in the soil can be removed by “cleaning” the root ball with a chlorine bleach drench (4 tablespoons of bleach per 1 gallon of day-old or rain water), or by submerging the entire root ball in a bucket of water for 30 minutes or more—air-breathing insects like ants, pill bugs, centipedes, etc, will either float to the surface or drown (some critters can “hold their breath” longer than others).

A mild infestation of mealybug or scale can be treated by removing any pests you see with a cotton swab dipped in rubbing alcohol. Treated plants should then be isolated and watched carefully for signs of re-infestation, removing any new pests until the population has been completely eradicated. Some fuzzy or very thin-leaved plants will be damaged by contact with rubbing alcohol, so test a leaf before treating the entire plant.

For heavier infestations of mites, mealybug, scale insects, and other piercing/sucking plant pests, we recommend the finer horticultural oil sprays. These should be applied outside in shade, and allowed to dry before bringing the plant inside. These refined oils are safe on most house plants, but would damage fuzzy-leaved plants like African violets. Some plants may suffer minor cosmetic damage (e.g., ferns and palms).

Another relatively safe product to use on house plants is insecticidal soap. While some plants may show leaf discoloration, most house plants do not. A soapy water bath is a great way to treat mites on plants that are small enough to turn upside down (pack paper towels around base to contain the soil) and swish their leaves and stems around in the suds. Let the soap dry on the plant. Soapy water can also be sprayed on leaves and stems and allowed to dry. Protectthe soil with paper towels to prevent soapy water saturating the root ball, as this can cause the soil to retain too much water.

To control flying insects like fungus gnats and whitefly, agitate the plant outside and then bring it in quickly before the insects can settle onto it again. For fungus gnat larva in the soil, use the chlorine bleach drench mentioned above. For white fly eggs, check the undersides of leaves, especially the lower leaves, and, using a damp soapy sponge, gently wipe away the eggs (grayish-white ovals). For monitoring or control of flying pests, yellow sticky bars (also called whitefly traps) can be placed near the plant.

For plant diseases like powdery mildew, botrytis, black spot and other fungi, you can try an insecticidal soap formulated for this use. One home remedy is to dissolve baking soda in water and spray the foliage (4 teaspoons per gallon of water, adding a few drops of dishwashing liquid). Good light and air circulation will help control fungus inside.

If you decide to use a chemical insecticide or fungicide, choose one that is formulated to treat your specific problem, and be sure to read and follow all label directions. Using the wrong chemical wastes money, exposes you and the environment to unnecessary risks, may further damage a struggling plant, and encourages pests to development immunity to overused products.

Fall is not the best time to repot unless a plant is desperate for more space. Most indoor plants slow their root and foliage growth over the winter. If you do repot, choose a container only 1 inch larger in diameter.

Plants will have to adapt to the different environment of shorter days and dry centrally heated air. Consequently, water use by the plant will change, so be sure to check carefully for dryness before watering. If your home is very warm and dry, you may need to water more frequently; if cooler and dimmer inside, the plants may retain moisture longer. Only fertilize during periods of active growth.

For more details on house plant pests and their treatment, see “House Plant Care: Common Plant Pests” in our information archive.